What is the best way to know is $_GET['example']=="somevalue"?

Question

if((isset($_GET[example]))&&($_GET['example']=='somevalue')){ ... }

OR

if((!empty($_GET[example]))&&($_GET['example']=='somevalue')){ ... }

OR just

if($_GET['example']=='somevalue'){ ... }

I am asking that why I have seen many example where people check first if $_GET['example'] is set and then if $_GET['example']=='somevalue' ( first and second example above ). I don't understand why not just use the last solution ( if $_GET['example']=='somevalue' then $_GET['example'] is obviously set ).

This question refers to any other variable ( $_POST, $_SERVER, ecc ).

Answer 1

if((isset($_GET[example]))&&($_GET['example']=='somevalue')){ ... }

Is the right one, you want to know that the "variable" exists (or is set) in order to use it. Empty just checks wether it has data of any kind or not. For example:

<?php
$foo= 0;

if (empty($foo)) { // True because $foo is empty
    echo '$foo is either 0, empty, or not set at all';
}

if (isset($foo)) { // True because $foo is set
    echo '$foo is set even though it is empty';
}

if (isset($var)) { // FALSE because $var was not declared before
   ...
}
?>

Answer 2

The differences between isset and empty are subtle but important. They are most relevant when used alone. If you are checking that a variable exists and is a truethy value (e.g. any string that is not all spaces or 0s) you can use either interchangeably.

When to use isset

Use isset when it's important to know if the variable has been defined and is not null:

if (isset($maybeExistsMaybeNull)) {
    // variable defined and is not NULL
}

When to use !empty

Use !empty when it's important to know if the variable has be defined and is truthy

if (!empty($mightBeEmpty)) {
    // variable defined, and isn't "", " ", 0, "0" etc.
}

!empty is a great shorthand for exists and is something.

When to use array_key_exists

Use array_key_exists when it's important to know if the key exists and the value is of no importance:

if (array_key_exists('something', $array)) {
    // $array['something'] exists, could be literally anything including null
}

When not to use isset

If your code looks like this:

if (isset($something) && $something) {
    // code is shorter with !empty
}

When not to use !empty

If your code looks like this:

if (!empty($something) && $something === "") {
    // you meant isset. this is unreachable.
}

Then you're writing code that can't be executed

Code that throws errors is error prone

Avoid writing code that issues notices/warnings that you are ignoring. For example in the question:

if((isset($_GET[example]))&&($_GET['example']=='somevalue')){ ... }

The first use of example is an undeclared constant. Or is it undeclared - what if you've got define('example', "foo"); somewhere else in the code.

if($_GET['example']=='somevalue'){ ... }

If the url doesn't contain ?example=.. that's going to issue a notice too.

Writing code without displaying errors means you can very easily miss mistakes like the first.

In context: isset and !empty are equivalent

For the example given, these two language constructs act exactly the same.

There is no case where one will act differently than the other, neither will issue a notice if the variable is undefined, and no measurable difference in performance between the two.

Answer 3

As others have said for checking things like $_GET and $_POST you would ideally want to use:

if ( isset($_GET['example']) && $_GET['example'] =='somevalue' ) {

// process data

}

So you always want to firstly make sure that the variable has been set (and not set to null) or in other words exists. Then proceed to check if the variable contains the data that you were expecting. If you try to make reference to a variable which doesn't exist (by not checking isset()) php will give you a notice saying 'undefined variable...etc etc'.

If you wanted to find out if a variable is set but are not concerned too much by what then you could use:

if ( !empty($_GET['example']) ) {

// process data

}

But I would be careful about using empty() on strings in this regard as empty can behave strangely with string data like '0' or ' '.

So I would always do the first one, to a) make sure the variable exists and b) is what you were expecting it to be.

Answer 4

This is something that you'll probably do a lot of and it helps to put together a class/functions which handles this checking for you so you dont have to do it everytime.

function checkValue($key, $value) {
    if(array_key_exists($key, $_REQUEST)){
        if ($_REQUEST[$key] == $value) {
            return true;
        } else {
            return false;
        }

    } else {
        return false;
    }
}

I just use Request as a default instead of switching out (though it is preferable to switch in some cases between POST and GET for security (imo)).

Now you can just call this function anywhere if (checkValue('Item', 'Tom') === true){} etc

Answer 5

the best is

if((isset($_GET[example]))&&('somevalue'==$_GET['example'])){ ... }

The difference between

'somevalue'==$_GET['example']

AND

$_GET['example']=='somevalue'

If you mistype the == and type = instead, the first notaion will raise an error to notify you.

Answer 6

if((isset($_GET[example]))&&($_GET['example']=='somevalue')){ ... }